Pump



cial requirements.

Figure lis a side elevation View of a mine arm y incorporating my invention, parts of which have been broken away to disclose the pump mecha-v nism contained therein.

Figures 2, 3 and l4 are transverse sectional views* through .the .ming armand pump mechanism taken along lines 2-2, 3 3, and 4-4, respectively, of Figure 1, as viewed'in Ithe' respectivey;v

directions indicated by the arrows.

Figure 5 is a longitudinal sectional view through Y a portion of the mine arm, showing partrof the-g pump structure in elevationuand YFigure, 6 is a transverse sectional view on line 6-6 of Figure 5...

Figure 7 is a diagrammatic view of the various elements of the pump assemblyto'illustrate the l its sevoperational relationship and function lof eral components. y i As stated previously, it lspreferred that the 1 pumpassembly'be housed'in the mine larmjl, 3 particularly because itwis `usually disposed in a substantiallyl horizontal position. possible, however, to locate the pump mechanism in the,Y mine column VBancliored in upright posii tion in the mine. shaft if that were preferred. 1 The mine arm is supportedinthe conventional manner by a clamp I0 and positioning collar ll securedv upon the mine bar. n

isfsecured in the desired position lengthwise of It .would be The drill 2 ih turn.

the-mine armk by a clamp 2.`The mounting cone 2l'may be clamped between blocks 22 to hold the -drillinv any adjusted angular position, acg cording to conventional practice.

The mine arm l is usually tubular, and inrthis i instancelikewise, of course, is hollow, but it has v special features ofconstruction to adapt it vmore conveniently for installation of the pump mechai nisrn. .'lhus van annular shoulder integralwith the' inner. vsurface of the. mine 4arm forms an l abutment l 2 which divides its interior into a resbore 40 in v.block 4, which constitutes. one hyseenin Figure V1*,and apump mechanism ,housmgl/space I4 within its right end.` #The left end f ofthe minearm may `be yclosed by a capy I5, arid its upperside hasa lling opening i6 pro- 1 vided with a strainerandnormally closed by a plug, Vas indicated inA brokenV lines'in 'Figure Il.`V

j The pump mechanism is assembled into the space m'within the rightv enc ofthe mine arm, which :isHangedforattachment to a mounting blockllby machine screws I8.v Abutment l2,

engaged by the pump assembly, limits the extent ofits -movement into the arm. A set screw I9 fitting in a keyway ,along the upper side ofthe mechanism may be employed to establish the of, the stepped piston. Thecentral portion of lthe piston is the largest and slidably fits a cylindrical bore 5D ,in` block 5, the axis of which is offset; from the axis of the cylindrical block, as

shown; in Figure 3. The left end4 30 and the right -end 3| of the piston are. of the samesize, both being much smaller than itsgcentral portion, `toiform hydraulic pump plungers.H AtA its/junc-` tion; with, such] plungersthe `enlargetl central".V

portion of the piston has annular surfaces disposed in radial planes, constituting pressure faces against which air under pressure admitted to cylinder space 5l) alternately at opposite sides of the enlarged portion of the` piston may press to drive the piston for lengthwise reciprocation.

The piston :plunger 30 is slidablyl received in a draulic liquid pump cylinder, while'a similar bore VB!! in block 6 slidably receives the other reducedV vnend 3| of the piston and constitutes the second hydraulic pump cylinder.

. The other main component of the pump assembly is the cylindrical valveblock 1, which incorporates a rather conventional annular reversing valve l0, operable to control the supply of air to cylinder space 50 for reversing the direction of travel of piston 3 automatically at each end of its stroke.

Before discussing the preferred construction of the-pump mechanism in further detail it will be helpful to have an'understanding of the operative relationship and function of its various elements, which may be acquired most readily from the diagrammatic illustration of the system embodied in Figure 7. I n

Hydraulic liquid, such as oil, under operating pressure is supplied to the drill through a short flexible hose from a connection23 communicating with the pressure duct P of the pump. Hydraulic liquid is returned'from thepump through -a second short flexible hose to the connection 24 leading into return duct R 'of the pump which communicates unobstructedly with reservoir |3. A supply'duct S connectsthe reservoir with the pump cylinder spaces V40 and 60, in which they VIn addition, passages through valve .block 'I` 4 and blocks 5 and 6 convey air between the valved passages and air cylinder 50 for the dual purpose of reciprocating piston 3 and automatically shifting valve I0 to effect such reciprocation.V This valve, it will be noted, is of the sleeve type, and is guidedl for axial shifting by stepped, generally conical inserts 1I which seat in the endsv of valve block 1 and are held together by a machine screw l2. Valve v10 is formed internally to slide on the shank'of screw 'l2 and on cylindrical portions of inserts 1l. Moreover the valve and such inserts are complementally yshouldered to limit the endwise travel of the valve.

The external circumference of valve 10 hasV three lands spaced by two annular grooves. These lands and Y,grooves cooperate with lands 'I3 on block 1 toiforni seals'between theblock landsy and valve lands Vin registry'andY by-pass passages between adjacent blockgrooves around the intermediate block lands in registry with valve grooves. As the valve 'i0 is shifted from one end of its stroke to the other the valve Ygrooves in registry with block landsv forming by-pass pas- Y sages around them will be moved out of registry with such lands to ,close such by-pass passages. By the same movement, however, such valve grooves will move into registry with other. block lands forming different by-pass passages, which will directk the air flow through the valve mechanism to reverse the flow to air cylinder 50.

, Air is supplied to the central groove ofvalve block 1 through a conduit 'I4 connected toan external source of air underpressure. y With the parts` in the position shown inFigure 7 piston 3 has just begun its travel to the right, as indi;-

career-v cated-'by 'the arrow. tion 'by air under pressure entering the central groove of valvefblock'1 from conduit 14, passing around the valve lblock 'land :forming 'the' right wall 'of such groove into the adjacentblock .groove onl the lright from which duct 5l leads, and moving through such duct in the-direction of the :arrow to the left .endof air cylinder 50. Piston 3, forced-to the right by such air pressure on the left annular surface of its enlarged .centrol lportion, zs'cavenges air `from the right end of .airfcylinder 5B through duct 53, which is connected to ith'e right `groovelof valve block `1, and through duct 52 `communieating with the groove of valve block Il adacent `:its central groove on the left. "From the latter vgroove such air Ibypasses the valve block land forming Vthe 'left Wall of vsuch groove, by way of the left .groove of valve 1.0 in registry withsuch land, into the adjacent valves-block vgroove on `the left, vand thence l,out :to the atmosphere through :a lport 1:5 in ythe lower side of :the 'block to the vleft of its ,center leading from such groove.

forced through .duct v5-3 by the vinitial movement ,of piston f3 to the right passes into the groove of valve block 1 yfarthest, to the right, to which 'the right end of rsleeve valve 1'0 is eX- pos'ed. Such .pressure tends to hold the valve to the :left in the position shown, although it is slight .because air is .bled from this block groove through asmjall aperture into the right duct T5 which leads to the atmosphere. Flow through duct :5.3 .does not 4continue for long, Abecause its opening rinto air cylinder p50 is uncovered just before :the piston 3 ,reaches the end-of its stroke to the left, and .consequently is again covered almost immediately after the commencement of the ipistonxs stroke to the right. Throughout such stroke, however, v'the :piston continues to force air from the right :end of :air cylinder '50 throughfduct=52- The Ycentral portionof valve v sliding ion bolt 12 :interconnecting 'inserts f1! is 'considerably shorter than :the spacing between ythe inner ends of such inserts. Ports 15 extend through the valve wall to establishA communication between the respective valve grooves andthe corresponding spaces vat opposite sides of `the central inwardly projecting annular rib Yof the valve. The end surfaces 11 of such -annularrib constitute piston `areas which are also utilized to assist `in maintaining the valve in its proper position even after tpassage 53 has-been closed by piston 3.

With the valve in the position .show-n, therefore, .it will be seen that the right .port 16 `is in communication with the centralblock groove and the lgroove adjacent to it on the right, through which'grooves flows air under pressure from conduit 14. Such 4compressed air is admitted to the right piston surface V11 of the valve by Way of right port 16, which will hold the vvalve vat the left fend of its stroke since the left vavle piston surface 11 is in communication with thefatmosphere through the left port 16 vand the valve block groove with which .the left atmospheric port 15 communicates. Y Y During movementof piston 3 to the might, the volumeof the 4left hydraulic .liquid cylinder -40 will beincreased `by the withdrawal of :piston sternv from it. Such volumetric `expansion will draw Voil vfrom the reservoir I3 through the `p0rtonvof supply duct S in block 4 andpast acheck valvef4| intohydraulic cylinder 40. Simultaneouslythe volume of the other hydraulic liquid cylinder 60 `in 'block ,-6 ,will be ,decreased :by-move-V ]Et -is vdriven in `this ,direc-f 6 mentor-plunger 3l intofit.v The oil in this 'cyli inder, zfilled during the immediately previous stroke of piston`i3 `to 'the left, 1 cannot pass back through the' supply -rduct Sin l"block '6 tothe reservoir: |13 past rcheck valve 6I'. 'The pressure fexl. erted on this oil by piston plunger 3| therefore forces 'open check valve .62 inV pressure :duct P.

,Suchpressure reacting through the portions of l duct vP in @blocks 4 and 5 also holds check valve 42 closed, vand the oilA under pressure is delivered through hose connection 23 to the pressure side of the drill feed mechanism.

As piston 3 nears the end of its stroke toward the right; which position :of the piston is'indicated A:by Abroken lines, it will be seen that the end of duct 54 communicating with aircylinder 50 will -be `uncovered by movement past it of the left veend .of the enlarged piston-portion. Atthis time .air `under pressure is still being supplied t0 the kleft end of air .cylinder 250 through duct 5I, so that part of this Aair Awill pass through the air cylinder and duct 54, as indicated by the broken .line arrow, into the groove `of valve :blockl 1 farthest to `the left. Although this Vgroove communicates with the left `atmospheric yduct* 15 through va 'small aperture, such aperture is sufficiently small -fso Ithat va substantial `pressurewill be produced in this groove. Such air pressure willactupon the left endof such valve`10,which ls exposed tothe'airingsuch groove, to overcome thejpressureion right piston zsurfacell and shift the valve to theright lend of Aits stroke.

By; such movement :the `central land ofl the,

valve will sever communication 4between air supply conduit 14 and duct 5I, while simultaneously the left lvalve groove will be `moved into registry with the valveblock land vimmediately to the left ofthe central groove, so that air may lbypass this land from air supplyconduit 14 to duct 5 2. Such valve movement,r therefore, has re-l sulted -in interrupting the supply of air under pressure to the left end of air cylinder 50 and supplying airunder pressure tothe right end of whichvduct V5l and right duct 15 communicate,

respectively.

V:Since .the ysupply of air under pressure to the left Yend of air cylinder 50 vhas thus been interrupted, and instead a supplycf compressed air to its right end established, lwhile at the same time its leftend has been `vented to atmosphere, movement of the rpiston Vto the right will ycease and lit will :be `driven toward `the left. During this movement air at first 'will be forced from the leftend Yof the air cylinder through ductv 54, exerting some pressure tending to hold valve "10 in its eXtreme right position, and air also .Will'be forced out throughduct 5 l Air Apassing through duct 54 will flow through the bleed ori-ce ofthe left valve block groove Ainto the left atmospheric duct 15, while the air nowingthrough duct 5l will be discharged Vthrough the ,fright atmospheric yduct 15. Until piston `3 has moved to the .leftzsuiiiciently so ltha't its `right leased.

Y 7 face passes -beyond the cylinder 50 valve 10 will nowbe heldin itsright position by airl under pressure'passing from' the centralgroove of valve block- I through the leftv valve groove around the valve block landV imma-.vr diately left ofcenter, and'through theleft valve` Y aperture 'I6 to exert pressureV upon the left innery valve shoulder TI. The right valve'port 'II..will, of course, communicate with the right atmos-l pheric duct 15, so thatv the right inner valve shoulder 1'I will be subjected only to atmosphericv pressure.

*During such movement of piston 3 to the left,`

the Yvolume of. the left hydraulic lliquid cylinder 40 will be decreased by movementof piston plungerv 30 into it. The'increase in pressure on the oil.Y will` hold check valve 4I in the Vsupply line S closed, but will open check valve 42 in the pressure line P. Such pressure will act upon check valve 62 in block 6 to close it and'hold it closed, so that the oil under pressure will now be delivered from cylinder 40 to the pressure side `of the l ow of air throughduct 53,-to reverse the piston stroke, as previously explained.

. It will be appreciated that the reversal of pis-v ton 3 by automatic shifting of valve 10 inthe manner explained will be effected 'instantaneously.v Consequently, although delivered alternately from cylinders I4 and 60, oil will now almost una interruptedlyffrom outlet 23, and because of its resilient nature, the hoseV connected to the outlet will expand under pressure and contract upon opening of ductj53into air;v

l the-tendency of the oil pressure to'decreasesuiciently to maintain oil delivery to the drill at` substantially constant pressure, tofeed the drill 1, l continuously and smoothly. As oil is supplied to l the pressure side ofthe drill feed mechanism oil l will. be discharged from its relief side through y l hose connection 24 and duct R of the piunp back j to reservoir I3. The rate `of oil delivery may be I governed as desired by throttling the flow of air l to the pump piston 3 to regulate-its speed of reciprocation. For this purpose a valve 18 may be adjusted to vary the size of the air inlet opening i through passage 74.

` Drain ducts D, one from oil cylinder 4I) and the other from oil cylinder 60, drain back into the reservoir through return duct R oil which may be forced past plungers 30 and 3I, respectively, i and collect in grooves 43 and 63. Between these grooves and air cylinder 5I] are additional grooves l 44 and 64, respectively, vented to the atmosphere j through a duct A which communicates through the. groove of valve block l secondfrom the left,

l from whichrgroove the left atmospheric duct 15 leads. Air tending to blow by plungers 3B and 3I into lcylinders ci? and', respectively, is thus re- Y 8 vantage:A proper relative'sizes of Vthe several conduits hadv Y to'be kept in mind as well as the problem of fabri-v eating-and assembling the various parts." To solve this problem the pump mechanism is composed offour cylindrical blocks, all of the same diameter and tted together in end abutting engagement. Three of these blocks 4, 5 and 6 house the pump'mechanism, and the fourth block 1 contains the valve mechanism. Y

As mentioned previously, the axis of the com-g posite 'piston 3 is olset lfrom theV axis of the cy lindrical blocks 4, 5 andUIi in which the piston andplunger cylinders are formed. Such eccenl tricjdispo'sition of the piston and cylinders prof vides space for the pressure supply duct S and return duct R, as shown in' Figure 3. If'desired,` for a given diameter of the blocks 4, 5and 6a somewhat largerair cylinder and larger oil ducts may be employed if the return and the suc@ tion ducts are combined. Instead of iiowing into the reservoir I3, therefore, some of the oil may iiow directly from the return connection 24'int0v the oil cylinders 40 and 60 through aV single duct serving for both return and suction. The only change necessary inthe construction shown would be to eliminate the passage R and to lead the port for rconnection 24 directly into the suction bore S of block 6. The space within the ,block could .be utilized to better advantage, of course, if the bores were rearranged slightly in such event. l Y i .n.-

Because the body 0f the pump is formed in three parts the necessary bores may be drilled in the several blocks quite readily. Preferably block 4 has an end boss 45 and block 6 has an end boss 6,5 which will t into theopposite ends of the air cylinder 50, as shown in Figure y1.

This interengagement of the three blocks, in conjunction With the arm I, itself constitutinga casing, will locate all the passages inproper reg'-V istry and relieve the reduced ends of piston 3 ofv Will be straight, so that the locating pin I9 may hold them all in proper rotative position with re'- lation to the mine arm I. lBefore the valve block 'I Vis, put in place a dowel pin E6 may be fitted into block 6 to interconnect these parts to hold Y them in registry for alignment of the cooperating sections of'passages 5I, 52,53, 54 and A. When the screws I8 are now drawn up the Yblocks will all be clamped tightly together between shoulder I2 andthe boss on blockv AI'I-tting within the end Y ofthe mine arm. With the partsin this relation- A problem in the actual construction of the pump unit was to make room for the various passages between the valve assembly and the air ship air supply duct 'I4 will register with a passage through block II which communicates through the valve 'I8 with the air supply connec-v tion'IB attached to such block.

The convenience of such a pump assembly will be evident. Being carried by the mine arrn,`th'e only additional element` required is the air sup# ply connection 'I9 from any convenient sourceof compressed air. Normallyy this connection'will be in 'the form of a hose, so that the arm I" may be raised or lowered'or rotated on the column B as `desired merely by loosening clamp I0, ad-

justing the mine arm, Iand then again tighteningV it. Additionally the drill support 2 may be shifted outward jalongV Vthe mine arm, or inward almost tothe column, because of the location of the sup-'l` 'In *devising theipump mechanism the .ae-16,312I

ply and return. ttings 23' andV uclosegtoz the. column,V and the ilaiibilityof: the conduits between suchzsu-pply' and return connections andethe" drill. These,- hosesf are short, so that they will `notA be in the way ofi the operator.' Despitefthese. advan tages the pump: is. of adequate. capacity' to' feed the'drill.effe'ctivelycand may be takenV apart quick- 1yl whenever' desired for. cleaning, for repair or for replacement off parts..

I. claim4 as: my invention:

1. In, combination, a mine column, tubular drill supportingy mea-11s a drill supported by saidy drill supporting means', axpumpi unit substantially housed. within said. tubular drill supporting means and conduit means interconnecting said pump unit and said drill forsflowor fluid under pressure from said. pump unit to: said.. drill.

2. In combination, a mine column, a tubular mine arm; extending laterally from. said. mine column, drill supporti-ng` means secured. to= said. minei arm,V a drill supported byv said drill supporting means, a hydraulic pump unit housed within said mine. arm, and. conduit. meansiinter.n connecting said pump unit and. said drillior. 'flow of liquid under pressure from said pump unit to said drill.

3 In combination, supporting means; a drill supported by said: supporting means, a continuously rotatable. hydraulic. drill-rotating; motor connected. to. rotate. said'. drill', an intermittent f delivery hydraulic: pump. unit supported by said supporting; means in a. position adjacent to saidv drill rotating moton. and short resilient. conduit means, directly interconnecting; saidj pump unit and. said drill-rotating motor, and operable.v by reason of. theirI resilience to deliver a; constant flow of liquid to saidV drill-rotating motor under substantially constant. pressure, although receiving liquid from said pump unit intermittently, thereby to eiect substantially uniform. rotation ofA said. drill-rotating. motor andsaid drill..

l 4. In combination, amine column, a mine arm` extending laterally from saidf mine column, drill supporting means secured tov said' minel arm, a drll supported by said drilll supporting means; a double acting intermittent delivery hydraulic' pump unitl housed Within` said mine arm', and a shortv resilient. hose interconnecting said pump unit and said drill, andope-rable by reason of its resilience to deliver a constant ow ofliquid to said' dri-ll under substantially constant pressure, although receiving liquidv from, said pump unitv intermittently:

5^. In combination, a mine column, amine arm -z extending laterally from said mine column and having a liquid reservoir in the end thereof rea 'mote' from said: mine column, drill supporting means secured to said? mine arm', a drill supported by said drillsupp'orting means, ahydraulic pump unit housed within the end' of said. mine arm. adjacent to` said mine column', and conduit liquid-1 therefrom` toi said drilL 6.. In combination, amine..- colurx'nr,` amineA arm extending laterally from saidl miney column. and

having a liquidreservoir in then end thereof' remote from said mine: column, drill supporting means secured: to saidmine. arm a. drill supported f by said drill supporting means. `an air: driven hydraulic pump unit housed within` the: end of said mine arm adjzacentftoisaid mine colummconduit means. interconnecting said drill and the.V

end of said; mine arm adjacent to said mine col.

umn, and-communicating with'. said, pump Aunit for `flow of liquidv therefromto f saidgdrilly, and.

means carried by thef'end of saidmine armV adjacent to saidr mineV column operatively connected.' to saidA pumpA .unit for regulating the supply-.ot air thereto toK vary the-delivery of liquid there from' to said' drill at. will.

7*. A pump unit comprising,v a general-ly cylin drical casing yhavingav reservoir in one: end:A

thereof, a generally cylindrical control valvetbody. tting. closely within the opposite `end of. saidI casing, air control, valve means insaidA control valve body, a generally cylindrical pump bod-yrv interposed between such reservoir and; said conf` trol. valve body and having. a. pump; chamber therein, pump means in such pum-pv chamber.. and a-i-r motor means insaidipump-fbody andfoperatively connected to.- said. pump. means to drive thesa-me, said. pumpbody and said control valve.. body having air duets therein establishingcom-- munication between-said control valve meansand said. air motor means; and: saidipump body havingducts therein establishing communication bel tween-. the reservoir, and the. pump chamber, and forming. axdeliivery passage for dischargeof liquid. underv pressure from*y the. pump: cham-ber,

8. A pump. unit comprising aY generally cylinn dricalw pump body having a pum-pchamberthere.; in, pumpmeans iny suchfpump. chamber, air motor means in saidY pumpv body and operativelyconneeted to.- said pumpA means to drive the sama.. said pu-mpbody having air ducts extending there-4 through for supplying air. to said air motor means for operating the same, a cylindrical controlvalvcl body disposed.. substantially in axial aligmnent. with said-pump body, and air controlivalve means in. said. control yvalvebodyf, said control. valvel body having air ducts therein establishing, communiecla-tion# between said air control valve meansand such air ducts in said. pump-body for controlling thes supply` of air tor said. air motormeans, and said. pump body havin-g therein... further ducts communicatingA with such pum-p chamberv for sup-y plying liquid thereto and for deliveryV otliquid.

. under, pressure. therefrom'.

. pump body',l and duet means disposed wholly within and extending lengthwise through saidpump body alongside `such elongated cavity adaptedtocornmunicate with both of such. pump chambers for supply' of. liquid thereto, and. open-` V ing directly intoz said reservoir.

l0; Apump unit. comprising a; generally cylinzf drical. pump` body' having` therein a. generallyr cylindrical cavi-ty with its axis offset toA one; side` of the. axis of said pumptbod-y, a pumpy element reciprocable axially of such cav-ityy and received l 'generally midway between the ends thereof to define a pump chamber at each end ci the'pumpbody cavity, means operable tov reciprocate said pump element, and duct means extending length'- wise.. througltiV said. pumpA body offset generally to the opposite side of its axis from the. axis ofthepump'body cavity, and adapted' tocommunicate with both pump chambers for flow of fluid.. be-

tween said. duct. means and lboth ci said. pump chambers. 'p Y y arm adjacent to said mine-column, and having therein a generally cylindrical pump chamber with itsl axis offset to one side of the axis of said pump body, pump means in such pump chamber, a delivery conduit and a return conduit interconnecting said drill and the end of said mine arm adjacent to saidA mine column, and duct means offset generally to the side of the pump body axis opposite the pump chamber axis, and establishing lcommunication between the reservoir. the pump chamberfand said conduits, for supplying liquid to the pump chamber, delivering liquid under pressure therefrom to said drill through said delivery conduit, and for return of liquid from said drill to the reservoir through said return conduit.

, 12. VIn combination, a mine column, a cylindrical'mine arm extending laterally from said mine column and having a liquid reservoir in the end thereof remote from said mine column, drill supporting means secured to said mine arm, a drill supported by said drill supporting means. a cylindrical pump body fitting closely within the end of said mine arm adjacent to said mine column, and having therein a generally cylindrical pump chamber with its axis offset to one side oi the axis of said pump body. double acting pump means in such pump chamber, and a resilient delivery conduit and a return conduit intercon-` necting said drill and the end of said mine arm adjacent to said mine column, said pump body having ducts therethrough offset generally to the s ide of itsfaxis opposite the pump chamber axis, and bestablishing communication between the reservointhe pump chamber. and said conduits, for supplyingzliquid to the pump chamber, deliv` ering liquid under pressure therefrom to said delivery conduit and for return of liquid from said drill to thereservoir through said return conduit,

said delivery conduit operating by reason of its resilience to deliver a constant now of liquid to said drill underl substantially constant pressure although receiving liquid from the vpump body ducts intermittently,

l 13. A pump unit comprising avpump body in` cluding three cylindricalblocks disposedin axial' alignment, the central block having therein an Vair chamber and the blocks at opposite ends thereof each having therein a pressure liquid chamber, all such' chambers being disposed in alignment, a composite piston having portions slidably fitting in each of such chambers, a cylin-` drical valve body disposed in axial alignment with said pump body, and automatic reversing air valve means in said valve body, said pump body and said valve body having registering air ducts therethrough establishing communication between said valve means and the air chamber VVof the central pump body block, and said pump body having therethrough a passage communicating with posed in axial alignment and tted closely within said cylindrical casing, the central block having therein an air chamber and the blocksat opp@ the central pump body block, and said pump;

site ends thereof each having therein a pressure liquid chamber, al1 such chambers being disposed in alignment, a composite piston having portions slidably tting in each of such chambers, a cylindrical valve body disposed in axial alignment with said pump body at the end thereof remote from the reservoir, and automatic reversing airA valve means in said valve body, said'pump body and saidV valve body having registering air ducts therethrough establishing communication between said valve means and the air chamberof body having passages therethrough establishing communication between the reservoir and both of the pressure liquid chambers, and defining a passage communicating with each of the pressurev liquid chambers for discharge of YVliquid under pressure therefrom.`

15.` In combinatiom'a mine column, acylindrical' mine arm extending laterally from said mine column, and having a liquid reservoir in the end thereof remote from said mine column, drill supporting means secured to said mine arm, a drill supoprted by said drill supporting means, a pump body including three cylindrical blocks disposed in axial alignment and fitted closely.

within said cylindrical mine arm adjacent to said mine column, the central block having thereinan air chamber, and the blocks at opposite ends thereof each having therein a pressure .liquidchamber, all such chambers being disposed in alignment and their axes being offset to one side of the'axis of said pump body, a composite piston having portions slidably fitted in each of such chambers, a cylindrical valve body disposed' in axial alignment with said pump body and at the end thereof remote from the reservoir, automatic reversing air valve means in said valve body, and

a delivery conduit and a return conduit intercon nesting said drill and the end of said mine arm adjacent to said mine column, said pump body and said valve body having registering air ducts therethrough establishing communication between said valve means and the air chamber of the central pump body block, and said pump body blocks having passagestherethrough oiset generally to the Vside of their axis opposite the axis of their chambers and establishing com-y munication between the reservoir, said conduits;

and both of the pressure liquidchambers, for supplying liquid to the pressure liquid chambers from the reservoir, delivering liquid under pres-- sure from Vthe pressure liquid chambers to said delivery conduit, and for return of liquid from said drill to the reservoir through said return conduit.

16. A pump unit comprising a tubular casing having a reservoir therein, a pump body fitted within said tubular casing, and having two pump chambers therein, two interconnectedl pump elements'one movable in each of said pump cham- Y bers, motor means housed within said casing and operable simultaneously to drive one of said interconnected pump elements into its pump chamber and and to withdraw the other of said pump elements outwardly relative to its pump chamber, and duct means establishing communication between such reservoir and both of such pump within said tubular casing, and having two pump chambers therein one adjacent to each end thereof, two interconnected pump elements one movable in each of said pump chambers, motor means housed Within said casing intermediate said two pump chambers and operable simultaneously to drive one of said interconnected pump elements into its pump chamber and to withdraw the other of said pump elements outwardly relative to its pump chamber, and duct means establishing cornmunication between such reservoir and both of such pump chambers, and further affording a delivery passage communicatingwith both pump chambers for alternate discharge of liquid therefrom, and a return passage communicating with the reservoir for return of liquid thereto.

HENRY S. HOFFAR.

REFERENCES CITED The following references are of record in the ille of this patent:

Number 15 Number UNITED STATES `PATENTS Name Date Magennis Jan. 14, 1941 Hirschberg Oct. 24, 1933 v Johnson Feb. 26, 1924 Lewis Nov. 17, 1936 Dix Jan. 26,1869 Cordell July 16, 1912 Rimailho Aug. 19, 1919 Vincent Sept. 8, 1936 Pfauser Oct. 20, 1942 FOREIGN PATENTS Country Date British Apr. 22, 1938 Certificate of Correction Patent No. 2,416,317. February 25, 1947 HENRY S. HOFFAR It is hereby certified that error appears in the printed speoioation of the above numbered patent requiring correction as follows: Column 9, line 11, claim 1, strike out a mine column, and that the said Letters Patent should be read With this (fr'eetion therein that the same may conform to the record of the ease in the Patent Signed and sealed this 13th day of May, A. D. 1947.

LESLIE FRAZER,

First Assistant Commissioner of Patents. 

